1. Field of the Invention
The invention relates to a roller positive displacement motor capable of operating with any type of fluid, either liquid or gaseous.
The motor comprises at least one motor unit having the following elements and features: a stator housing composed of a tubular body (stator ring) and two end plates.
The inner surface of the stator ring (stator surface) is a generally elliptical shaped cylindrical surface, the directrix of which is a displacement curve having a symmetry order of two with respect to its center,
a shaft rotatably supported within the housing;
a rotor fixed on this shaft, the outer surface of which rotor is a cylinder having a circular directrix (rotor cross section profile). A number n.sub.r of identical axially extending slots, opened in the outer surface of the rotor, are machined at equal angular intervals about the rotor. These slots are bounded on both sides by two plane faces parallel to a median plane, either radial or not;
cylindrical rollers, the number of which is n.sub.r, guided in the slots of the rotor, so as to remain in axial contact with the ring inner surface and to define in this way working chambers. Each of these working chambers has a volume defined by the stator ring surface, two consecutive rollers, and by the surface of the rotor, including a variable part of the volume of the slots wherein the rollers are moving.
One face of a slot is the leading face on which the roller is applied when it is driving the rotor, and the other face is the trailing face on which the roller is resting when it is driven by the rotor.
Inlet and outlet ports are bored in the stator housing and possibly managed with valves, to afford inlet and outlet of fluid.
A motor which, as described herein, comprises a single rotor and a single stator ring will be referred to as a motor unit. A volume comprised between the rotor, the stator ring and the two end plates will be referred to as a working chamber. As will be described, the working chamber volume varies during operation of the motor unit.
As the ratio of the length of the rollers to their diameter is of course limited to insure their convenient guiding, it is necessary to employ a multiple unit motor" if this motor must have a great displacement without having too large an external diameter and too great a sliding velocity of the rollers on the stator surface.
A motor comprising a k number of motor units uses obviously k rotors fixed on the same shaft and a stator composed of k stator rings, of (k-1) intermediate stator plates, each of these plates separating two units, and two flanges working as end plates.
2. Description of the Prior Art
Roller displacement machines, operating as liquid pumps, have been described and are produced. They have, as often as not, a liquid distribution organisation quite close to that of a vane machine, and the rollers are formed to have a necessary large clearance with respect to their guiding slot so that they come into contact with either one or the other face of the slot, enabling the roller to work as an internal distribution element, attempting to avoid a situation where some volume of the liquid can be, at one moment of its evolution, enclosed in a closed working chamber, the volume of which is reducing. Practically, this desired does not seem to be reached exactly, and temporary overpressures occur in known pumps (refer to patent GB-No. 2.028.430-A).
Experience demonstrates that this type of pump cannot be converted into a hydraulic motor. When inlet and outlet ports are reciprocally exchanged, the torque supplied by the shaft of the machine varies quite irregularly with the rotation angle of the shaft, and even, for some of the machines, reverses periodically.
Design requirements thus seem to be much more strict for a roller motor than for the corresponding pump, especially if the fluid with which the machine exchanges energy is a liquid. A pump is usable even when the torque applied to the shaft is strongly variable, whereas a motor is not suitable in the same conditions.
This is probably the reason why roller motors have been used and industrially produced infrequently. The only patent we know as related to such a motor in the U.S. Pat. No. 2,826,179 (KLESSIG). In the hydraulic motor disclosed by KLESSIG, the distribution of fluid is quite close to that of a vane machine. Furthermore, KLESSIG recites that the "driving elements" of his motor may be either rollers or vanes.